Biological control ofOstertagia ostertagiby feeding selected nematode-trapping fungi to calves

Abstract

Three nematode-trapping fungi, oneArthrobotrys oligosporaand twoDuddingtonia flagransisolates, were fed toOstertagia ostertagi-infected calves to test their ability to destroy larvae of this parasite in faeces and consequently to reduce the transmission of infective larvae to herbage. The fungi had previously been selected for their capability to pass the alimentary tract of cattle without losing growth and nematode-trapping potentials. Dung was collected from three calves each fed one of the three fungi and placed as 1-kg cow pats on a parasite-free grass plot together with control cow pats from a calf that was not given fungi. The cow pats contained comparable concentrations of parasite eggs. The twoD. flagransisolates were highly effective in that they reduced herbage larval infectivity by 74–85%. In contrast,A. oligosporadid not show any effect in the present experiment. Field experiments will demonstrate ifD. flagransrepresents a potential organism for biological control of bovine gastrointestinal nematodes under practical agricultural management conditions.